1. Field of the Invention
This invention relates to aircraft suspension and landing gear systems, particularly for use with helicopters, wherein the system vertical stiffness and damping are sufficiently high to attenuate landing impact loads and wherein the system roll mode stiffness and damping are sufficiently soft as to permit the avoidance of ground resonance instability.
2. Description of the Prior Art
In the aircraft suspension and landing gear art, serious compromises have been made in the past between the system stiffness and damping required for load impact attenuation and the conflicting system stiffness and damping required for ground resonance instability abatement, such that both purposes suffered thereby. This was so because the prior art does not include an aircraft suspension and landing gear system in which the system roll mode stiffness involved in avoiding ground resonance instability may be established independent of the stiffness of the system involved in landing impact attenuation.
While the structure of Holland U.S. Pat. No. 3,042,345 and Maltby U.S. Pat. No. 2,933,270 bear a superficial resemblance to the construction of this invention, it should be borne in mind that neither of these patents has a construction which accomplishes ground resonance abatement. The Holland patent seeks to obtain better aircraft controllability in cross winds and on sloping grounds and the Maltby patent is an active, servo actuated system with substantial roll stiffness.
Other prior art bearing a superficial resemblance to the aircraft suspension and landing gear system shown herein is directed to the problem of being able to land a helicopter on uneven ground while maintaining the helicopter level due to the accommodating motions of the landing gear.